The present invention relates generally to a pin retainer and flag for holding a pin in place with respect to pivotally attached structure members. More particularly, the invention is directed a pin retainer assembly for use on a tractor or similar work vehicle for providing a pivotal coupling between the tractor and an implement.
In the art of pin retainer and flag assemblies for holding a pin in a pivotal joint, such as for tractors and other work vehicles, a variety of structures have been proposed and are currently in use. Such arrangements typically include a pin that is removably fitted into a bore of a structural member, such as a clevis. Clevises of this type are found in many applications such as for coupling various mechanical linkages and actuators in a hitch, where pins and retainers serve to connect lift links and actuators to a rocker arm extending rearwardly from the tractor. The pin in such structures typically extends through a hole in a mating element, such as an actuator tang or a lift link end, aligned with the bore in the clevis to pivotally couple the structural member with the mating element. Conventional assemblies commonly include a pin having an enlarged head or other stop at one end which abuts the structural member on one side and a free end designed to be inserted through the aligned bores in the structural member and mating element. Once installed, the pin is retained in the aligned bores by various means, such as by a securing pin inserted into a through-hole in the pin adjacent to its free end.
Such pin retainer assemblies are designed to prevent axial movement of the retaining pin along its longitudinal axis to maintain the pin in its installed position in the assembly during operation and thereby to maintain the coupling between the members joined by the pin. Such assemblies typically also prevent the pin from rotating within the bore. Moreover, in certain applications, industry standards require that the retainer be permanently attached either to the structural member or to the pin so that the retainer will always be present and available whenever the pin is inserted to make up the joint. This is particularly true for ISO regulations regarding flagging mechanisms for work vehicle hitches. Conventional pin retainer assemblies are typically attached to the structural members by chains, cables and the like.
In many applications, the structural members and mating elements must rotate through some angle with respect to one another, for example, where retaining pins are used to couple an implement or various hitch elements to a work vehicle. This rotation may subject the pin to considerable torque tending to rotate the pin about its axis within the aligned bores. To eliminate wear between the pin and the bores in the structural members, it is often preferable to prevent pin rotation within the structural members or to selectively permit rotation within one member while preventing rotation within another. Several structures have been proposed to control retaining pin rotation while at the same time resisting axial movement of the pin. In one such structure, the retaining pin includes a flange fixed at one end, the flange extending along the structural member and being secured to it at a point radially outward from the pin, such as by a screw. An example of such an arrangement is disclosed in U.S. Pat. No. 2,967,726 issued Jan. 10, 1961 to Weston. In that assembly, a flange is rigidly connected to one end of a clevis pin such as by welding. The flange extends generally at a right angle with respect to the axis of the pin. To retain the pin and prevent its rotation, a cap screw extends through the flange at a point spaced apart from the pin and is lodged in a threaded bore in the structural member. The screw is received in the structural member in such a way that it may be deflected to a certain extent to absorb forces exerted by the flange as a result of torques on the retaining pin. However, the performance of this and similar assemblies is severely limited in that the screw must withstand essentially all forces acting between the pin and the structural member and transfer the forces to the frame in which it is fixed. In particular, the fastener must transfer all rotational forces transmitted by the pin to the flange. Such structures typically fail by shearing or other rupture of the screw as a result of these forces. A further disadvantage of this structure is that it requires a special tool, typically a screwdriver or wrench, to attach or remove the retaining pin.
U.S. Pat. No. 1,711,018, issued Apr. 30, 1929 to Ellis et al., discloses a spring bolt which is secured in a bore of a structural member at one end by a nut. At the other end of the bolt is a removable head in the form of a removable key that engages notches on the bolt. To maintain the head on the bolt, a recess, shaped to fit the head once attached to the bolt, is formed on the structural member. To prevent the head from rotating with respect to the structural member, a protuberance is formed on the key that fits into a similarly shaped portion of the recess.
This arrangement has several disadvantages. First, it requires a specially shaped asymmetrical recess to be formed to mate with the key, which presents difficulties from a manufacturing standpoint. Second, the assembly is difficult to use on a tractor or the like where frequent changes of the pin joint may be necessary. In particular, an operator must perform numerous steps for mounting the joint, namely, attaching the key to a first end of the bolt, pushing the bolt into the bore of the structural member until the key is received within the recess, and finally attaching a nut or the like to a second end of the bolt. Third, this design requires several separable parts that are easily lost, contrary to the requirement that all members of the retainer assembly be permanently coupled to the vehicle or to the pin. Finally, the threads on the bolt can be easily damaged when used in the field, making it difficult or impossible to thread the nut in place on the bolt.
Thus, there is a need for an improved pin retainer capable of retaining a pin in its axial position and preventing its rotation. It is an object of the present invention to provide such a pin retainer. It is a further object of the present invention to provide a pin retainer and flag assembly which affords easy mounting and removal of the pin. It is still another object of the present invention to provide a pin retainer and flag assembly in which all members of the retainer mechanism may be permanently coupled to a structural member without the need for extra coupling members such as chains, cables, wires, or the like.